13 May 2017

GPS

On 31st August, 1983, a Korean Air Lines Boeing 747 flew from New York headed for Seoul via Anchorage. After leaving Alaska in the early morning of 1st September, the plane was shot down just off the Russian island of Sakhalin by two missiles fired by a Soviet pilot. 269 people died in the incident including Larry McDonald, a congressman from Georgia.

The plane had drifted 300 miles off course and had been flying in Soviet airspace for two minutes prior to the attack. Someone in the cockpit had probably punched the wrong coordinates into the navigation computer. The plane was beyond contact with any air traffic controller.

Just four days later President Reagan issued an executive order directing the Department of Defense to release classified descriptions of the Global Positioning System (GPS) signal structure. A White House press release read: “World opinion is united in its determination that this awful tragedy not be repeated. As a contribution to the achievement of this objective, the President has determined that the United States is prepared to make available to civilian aircraft the facilities of its Global Positioning System when it becomes operational in 1988.”

World opinion may have been united but military opinion certainly wasn’t. Technically there wasn’t that much to Reagan’s directive as details of the GPS signal were already available to anyone who wanted to build a receiver that could read the code. But the military could always make this difficult or even impossible by changing the GPS signal. The administration’s directive was effectively a public statement by the executive informing the military that GPS was no longer theirs alone.

GPS had been developed over decades, often against the wishes of much of the military establishment. While its advantages seem obvious today the Air Force was never big on space and GPS involves the deployment of 31 satellites in orbiting 20,000 kilometres above the Earth. There are active atomic clocks aboard each satellite, which are synchronised within nanoseconds to the clocks on every other satellite, all of which obey the Master Clock at the United States Naval Observatory in Washington D.C. The satellites broadcast a continuous radio signal that carries information about where the satellite was and will be- and also the exact time the signal left the satellite. The signal travels 20,000 kilometres reaching us sixty-seven milliseconds later.

When somebody fires up a mobile phone almost anywhere on Earth the process is the same. Nearly every spot on Earth has a line of sight to at least four GPS satellites at all times. The GPS receiver in the phone searches for the four strongest signals. By noting each signal’s origin and its arrival time, the receiver can compute the latitude and longitude of the phone, and express it as a point on a map. The receiver can also provide the correct time. This gives an exact calculation of space and time.

Its first military application was to improve the accuracy of bombs and keep bomber pilots safe. Today its use stretches everywhere. GPS is now most familiar as the enabler of satellite navigation systems but all smart phones and tablets, some 3 billion devices, have a mobile app using some kind of GPS-derived positioning information. In the next two to three years that number is expected to double. The estimated value of the global GPS market is nearly $30 billion, but its economic influence is far greater than that if we factor in the GPS chips in smartphones, tablets, and computers, moving platforms such as cars, ships, and planes, and various products in service industries that would produce a value in the trillions of dollars.

GPS is used to track the movements of convicted criminals not in prison, sex offenders, dementia sufferers, wayward children and wild animals. GPS guides planes in the air and to the ground and locates ships at sea. People wear watches with GPS and buy specialised sporting applications for fishing and golfing. It is used to locate oil and mineral deposits and is increasingly used in crop production.

GPS is one of the world’s most accurate clocks and is also a clock that unites other clocks. Systems that require time synchronisation use GPS such as the electrical grid, and the mobile phone and financial trading networks. It helps predict the weather, surveys land and builds bridges and tunnels. It calculates how much water is in the ground and when the earth deforms. It senses the movement of tectonic plates to less than a millimetre. It can feel the glaciers melting as the planet warms up.

GPS is a global navigational system, or GNSS. It is highly complex and expensive to build and maintain so it has few rivals. All are controlled by nation states but only Russia’s GLONASS offers similar global coverage and a complete satellite constellation. The Galileo system being developed by the EU and the European Space Agency will not be fully operable until at least 2026, when the Chinese Beidou may also become fully operational.

Though less visible GPS’s influence on the world equals or exceeds the Internet. In fact the Internet could not operate without precision timing controlled by GPS. This may seem odd because while the Internet provides a ubiquitous database and a way to share information, GPS is just a radio pulse, first emitted by Sputnik in the 1950s. But that pulse has become like our own personal pulse. If it failed this weekend, the disruption to our society would be colossal. For better or worse, it forms an essential part of the infrastructure of modern life.

I say better or worse, not as a cliché, but because while there are undoubted examples of progress starting with President Reagan’s original motivation of wanting to safeguard innocent planes which strayed a short distance from their planned flight path, there are also clear examples of dangers caused by the widespread use of GPS.

As I said one of the first popular applications was the concept of Satellite Navigation, known colloquially as SatNav. At a moderate level its widespread use is causing people to lose the ability to read a map. Younger people may never even learn this skill as their mobile phone will do all the work for them. At the extreme level people have lost their lives because of an excessive reliance on SatNav. There are numerous examples of ‘death by SatNav’ where the driver simply follows the audio instruction even when this means driving into the sea or off an unfinished bridge or in one terrible case an elderly couple followed the SatNav instruction down a road that became a lane that became a track into the wilderness. When the car ran out of petrol the husband went off to seek help. The remains of his body were found years later.

But this lost ability to read maps may be more fundamental to our cognitive reasoning. The ability to navigate oneself, to have a ‘sense of direction’, has evolved over millennia and developed long before we were capable of drawing a map to read. Primitive man ‘navigated’ by the stars. We know that men were sailing in small canoes across vast stretches of the Pacific Ocean long before the sextant was invented. So this skill is not just a convenience, it is a fundamental part of how our brains work and the excess reliance on GPS information may be altering that for ever.